INCREASED SPECIES-DIVERSITY AND EXTENDED HABITAT RANGE OF SULFUR-OXIDIZING THIOMICROSPIRA SPP

We combined traditional cultivation methods and new molecular techniqu es to study the diversity and habitat range of bacteria of the genus T hiomicrospira. Specific primers were designed and used in the PCR to a mplify the 16S ribosomal DNA (rDNA) of Thiomicrospira spp. and thus de tect the presence of these bacteria in environmental samples and enric hment cultures, By using this genus-specific PCR, we were able to ampl ify 722-bp-long 16S rDNA fragments from different saltwater habitats a s well as from a freshwater ecosystem, Furthermore, we were able to is olate most of these bacteria in pure culture by using enrichment cultu res for chemolithoautotrophic sulfur-oxidizing bacteria, With denaturi ng gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA fragm ents followed by hybridization analysis with one of the primers as a g enus-specific probe, it was possible to monitor the success of isolati on, The combined approach resulted in the isolation of several chemoli thoautotrophic bacteria from different habitats: e.g., a coastal sedim ent along the coast of Chile, a microbial mat of the hypersaline pond Solar Lake (Sinai, Egypt), and the saline spring Artern (Thuringia, Ge rmany), In addition, four different isolates were obtained from sedime nt and water samples taken at Jadebusen, which is part of the German W addensea. Comparative analysis of the nearly complete 16S rRNA sequenc es of these isolates indicated several new species, all grouping with the Thiomicrospira species of the gamma subdivision of the class Prote obacterin, A freshwater Thiomicvospira species could not be isolated, but sequence analysis of the PCR product obtained after amplification of the environmental DNA with the Thiomicrospira-specific primers reve aled its phylogenetic affiliation, The study indicates an increased sp ecies diversity of Thiomicrospira and the ubiquity of this sulfur-oxid izing bacterium in habitats with reduced sulfur compounds.